1. Field of the Invention
This invention relates to a coupling used in orthodontic treatment to connect orthodontic appliances or devices together.
2. Description of the Related Art
Orthodontic therapy is a specialized form of treatment within the field of dentistry. Orthodontic treatment involves movement of malpositioned teeth to orthodontically correct locations. Orthodontic treatment often greatly improves the aesthetic appearance of the patient's teeth and also improves the patient's occlusion, so that when the jaws are closed the upper teeth are in proper positions relative to the lower teeth.
Orthodontic treatment is often carried out by a system of tiny appliances, wires and other components that are commonly known collectively as "braces". Typically, a small appliance known as a bracket is connected to each of the patient's anterior, cuspid and bicuspid teeth and an archwire is placed in a slot of each bracket. The archwire forms a track to guide movement of the brackets and the associated teeth to desired positions. Typically, end sections of the archwires are held by appliances known as buccal tubes that are secured to the patient's molar teeth.
In some instances, it is necessary or desirable to use coupling pins during the course of orthodontic treatment. Many of the earliest orthodontic pins were used to couple archwires to brackets, including certain types of orthodontic brackets that were known as "Begg" brackets. Begg brackets have an upright tube with a passage for receiving the pin, and the pin has a head that captures the archwire between the tube and the associated tooth.
Other known types of brackets are made with an auxiliary passage that can be used for receiving a pin for connection to components other than archwires. For example, brackets known as "vertical slot" brackets have a passage that is located lingually (i.e., in a direction toward the patient's tongue) of a slot that receives the archwire. Typically, the passage extends in a generally occlusal-gingival direction (i.e., in a direction along a reference axis extending from the outer tips of the teeth to the gingiva or gums), which may or may not represent a true vertical direction. Vertical slot brackets enable the orthodontist to install a pin in selected brackets as desired, and then subsequently use the pin to couple those brackets to other devices or appliances.
Buccal tubes also often have auxiliary passages that can be used if desired for receiving a coupling pin. Typically, such auxiliary passages extend in side-by-side relation to the passage that receives the end section of the archwire. Buccal tubes are especially useful as connection locations for orthodontic pins, because the relatively large roots of the molar teeth associated with the buccal tubes provide a strong anchor for moving other teeth during the course of treatment.
Orthodontic coupling pins have enlarged heads that serve to couple a device, appliance or other component to the pin and also serve to prevent the pin from moving in one direction through the passage of the associated bracket or buccal tube. Often, the head of the pin has a somewhat spherical or ball shape. Alternatively, however, the head of the pin may be somewhat "L"-shaped or "T"-shaped. In some instances, coupling pins are known as "hooks", particularly if the pin has an "L"-shaped head or a "T"-shaped head. Coupling pins used to connect archwires to brackets (such as Begg brackets) are often known as lock pins.
Orthodontic pins that are received in auxiliary passages of brackets or buccal tubes are sometimes connected to devices known as force modules that provide a compressive force, a tensile force or both. In some instances, force modules are used in intra-arch applications where one tooth or a selected set of teeth are moved relative to other teeth of the same jaw. In other instances, force modules are used in inter-arch applications where one tooth, a selected set of teeth or an entire dental arch is moved relative to the opposite dental arch.
An example of use of a force module in an intra-arch application is closure of a relatively large space between adjacent teeth as might occur, for example, if a tooth has been extracted or is otherwise missing. To close the space between adjacent teeth, the practitioner may elect to place a pin in the auxiliary vertical slot of each bracket adjacent the space, and then connect an elastomeric force module between the pins. The elastomeric force module exerts a tensile force on the pins and consequently on the associated brackets in order to move the teeth toward each other over a period of time to close the space.
A variety of orthodontic force modules used in tension for such space closure applications are known. Examples include ring-shaped modules (such as intraoral elastics from 3M Unitek Corporation) and dogbone-shaped modules having outer, ring-shaped ends with straight shank middle sections (such as "K" modules from 3M Unitek Corporation). Other examples include chain type force modules which comprise a series of interconnected rings (such as "C" modules from 3M Unitek Corporation).
The orthodontic treatment of many patients includes correction of the alignment of the upper dental arch with the lower dental arch. For example, certain patients have a condition referred to as a Class II malocclusion wherein the lower dental arch is located an excessive distance rearwardly of the upper dental arch when the jaws are closed. Other patients have an opposite condition referred to as a Class III malocclusion wherein the lower dental arch is located forwardly of the upper dental arch when the jaws are closed.
Orthodontic treatment of Class II and Class III malocclusions are commonly corrected by movement of the upper dental arch as a single unit relative to movement of the lower dental arch as a single unit. To this end, pressure is often applied to each dental arch as a unit by applying pressure to attachments that are connected to the patient's brackets or archwires. In this manner, the Class II or Class III malocclusion can be corrected at the same time that the archwires and brackets are used to move individual teeth to desired positions.
A variety of devices are used for treatment of Class II and Class III malocclusions. Examples include flexible members as described in U.S. Pat. Nos. 4,708,646 and 5,352,116. Another type of member useful in such applications is described in U.S. Pat. No. 5,651,672. U.S. Pat. Nos. 3,798,773, 4,462,800 and 4,551,095 disclose telescoping tube assemblies that urge the jaws toward positions of improved alignment.
Typically, orthodontic coupling pins are connected to brackets, buccal tubes or other appliances by threading the shank of the pin through the auxiliary passage until an outer end section of the pin projects past the passage. Next, the practitioner uses a pair of pliers or other tool having small tips to grasp the outer end section and bend the outer end section in an arc, such as a 90 degree arc. The pin can be removed when desired by straightening the outer end section into a position of coaxial alignment with remaining sections of the shank. Pins may also be connected to appliances by use of a deformable stop member that is clinched onto the outer end section of the pin once the pin is in place.
U.S. Pat. No. 5,718,576 describes an improved orthodontic coupling pin that is especially useful during treatment of Class II malocclusions. The pin of certain embodiments set out in U.S. Pat. No. 5,718,576 has an offset shank section that reduces stresses on the pin in use and consequently reduces the likelihood of breakage of the pin or other associated devices or appliances. Optionally, the outer end section of the shank has a reduced cross- sectional area that is smaller than cross-section al area than remaining areas of the shank, so that the end section can be readily bent by the orthodontist as needed after insertion of the shank into an appliance.
Additionally, some orthodontic devices include a coupling that comprises a pin or pin shank adapted to be received in an auxiliary passage of a bracket, buccal tube or other appliance. For example, pending U.S. patent application Ser. No. 09/06,746 entitled "MANDIBULAR REPOSITIONING DEVICE" describes an orthodontic device that includes a pivotal connector having a shank. Like the pins with the enlarged heads mentioned above, the shank of the connector described in pending U.S. Ser. No. 09/063,746 has an outer end section that is adapted to be bent in an arc in order to securely couple the device to a buccal tube or other appliance once the shank has been inserted into the auxiliary passage.